The bladder or urinary bladder is a muscular sac in the pelvis, located just above and behind the pubic bone. Urine is made in the kidneys, and travels down two tubes called ureters to the bladder. In normal operation, the bladder muscles stretch to allow the bladder to store urine. When desired, a person can normally voluntarily urinate. In a healthy condition, during urination the bladder muscles contract and two sphincters (valves) open to allow urine to be expelled. In both males and females, urine exits the bladder into the urethra, which carries urine out of the body.
Bladder paralysis can occur from compression of the spinal nerves roots, a condition called Cauda Equina syndrome. These nerve roots normally cause the bladder to contract. Cauda equine syndrome can be caused by a severe ruptured disk in the lumbar area, severe lumbar spinal stenosis, spinal injury from a fall, motor vehicle accidents, gunshot wounds, or infection. Also, a weakened bladder or a need for bladder removal can be due to bladder cancer. Bladder cancer is the fourth most common cancer in men and the tenth in women with an estimated 68,000 cases in the U.S. annually. Weak bladder can also occur from other medical conditions.
Many patients with bladder cancer eventually need to have the bladder removed, e.g. a cystectomy. Often the surgeon then creates a new bladder, referred to as a neobladder, from the patient's small intestine. Patients with reconstructed bladders after cystectomy are often unable to empty the neobladder because of a lack of muscle tissues inside the neobladder.
After a total cystectomy, the surgeon works to reconstruct the urinary tract in order to allow urine to leave the body. The surgeon has one of the following options:                1. He may use a piece of the patient's intestine to create a tube to run from the kidneys to the abdominal wall (Heal conduit or urostomy). The urine is collected in a bag worn on the abdomen.        2. A second option is what is called cutaneous continent urinary diversion (Indiana pouch). In this option, the operator creates a reservoir to the urine attached to the abdominal wall. The patient has to pass a catheter through the abdominal wall opening several times a day to empty the pouch.        3. A third option is what is called orthotopic continent diversion (Neobladder). The created pouch in this case is attached to the urethra. The patient will be able empty the bladder in a relatively normal fashion.However, the process of voiding with a neobladder in reality is far from normal. The neobladder does not contract. The patient usually has to learn several techniques, such as pelvic exercises, to increase the pelvic pressure to help voiding. In most cases the void is incomplete, leaving residual urine which puts the patient at risk of recurrent UTI (urinary tract infection). Most patients have to use intermittent self-catheterization to fully void. Further, a neobladder does not supply the patient with a feeling of a bladder filling or fullness.        
Studies have shown that normal individuals experience certain sensation patterns as the bladder fills, corresponding to increases in bladder pressure. Urodynamic studies in normal individuals show the following parameters; during the filling phase, abdominal and bladder pressures are recorded via rectal and urethral catheters, respectively, whereas detrusor pressure (Pdet) is calculated by subtracting abdominal pressure from bladder pressure. Initial resting abdominal and bladder pressures are 5-20 cm H2O in the supine position, 15-40 cm H2O in the sitting position, and 30-50 cm H2O in the standing position. Pdet in an empty bladder varies between 0 and 10 cm H2O in 90% of cases. Normal Pdet during bladder filling at a rate of 50-60 mils should be <20 cm H2O.
There are three basic normal bladder sensation patterns: (a) the first sensation of bladder filling, which is felt when the volunteers first become aware of bladder filling (it is vague sensation, felt in the lower pelvis, which waxes and wanes, and could be easily ignored for few minutes); (b) first desire to void, a constant sensation that would lead the patient to void in the next convenient moment, but still voiding can be delayed (it is felt in the lower abdomen and gradually increases with bladder filling); and (c) strong desire to void, a persistent desire to void without fear of leakage, and felt in the perineum or urethra. The volume thresholds when the sensations are felt are generally lower in women.
There remains a need for an apparatus which creates awareness of bladder fullness and gives the patient full control to void normally.